1. Field of the Invention
The present invention relates to a travel, cargo-handling, electric power steering, and battery liquid level monitor control system for industrial use vehicles (hereinafter referred to as a battery driven fork-lift truck) in which a regenerative battery recharging broke mode is provided when the travel direction is reversed. When an abnormal operating condition is detected an appropriate trouble message is displayed on a display screen by a microcomputer indicating the location of the abnormal condition.
2. Prior Art
In a conventional control system, individual control units are provided for travel, cargo-handling and power steering. To prevent interference between travel, cargo-handling, steering, and monitor display control circuitry, prior art control systems require multiple sensors and terminals for signal transmission/reception. Furthermore, the circuitry must be interconnected by many different individual control units. Accordingly, prior art control systems are complicated in construction and inherently involve the following problems:
(1) Because individual control units are used, it is difficult to prevent interference between them and combining them into a system is difficult.
(2) When travel and cargo-handling are concurrently performed, a large current flows and hence battery voltage drops. Insufficient motor power and instable control results.
(3) During braking kinetic energy is not reconverted into electric energy. In this respect, poor energy saving is attained. The large current flow through the motor tremendous brush and commutator wear. When energy regeneration is used in the prior art, an automatic regenerative/power travel check system with a very high response or a high operation feeling is required.
(4) A number of contacts to open and close circuits are used and full power activates these contacts. When these are activated, energy saving is not possible The large amount of heat generated also causes physical size of the contacts to be large and consumes a large amount of space. This is problematic when the components are mounted.
(5) Because individual control units are used to check whether or not parts are functioning normally or whether parts need maintenance, a single monitor of all the control units is impossible. Furthermore, prior art systems do not provide detailed monitor data in an easy-to-understand data format.